Non-insulin-dependent diabetes mellitus (NIDDM, type II diabetes) is characterized by abnormalities in insulin secretion and insulin action. NIDDM constitutes 90-95% of the approximately 6 million diagnosed diabetics in the United States. NIDDM is characterized by hyperglycemia, the result of insulin resistance in peripheral tissues (skeletal muscle and adipose tissue), where insulin-stimulated uptake/utilization of glucose is blunted, and in liver, where insulin suppression of glucose output is insufficient. These impairments in insulin action play an important role in the development of elevated fasting blood glucose and glucose intolerance.
Diet and exercise are first-line therapy for NIDDM patients. NIDDM patients also take oral hypoglycemic drugs to control blood glucose levels. The most widely used hypoglycemic agents are various formulations of insulin and sulfonylureas. A major drawback with these therapies is the occurrence of potentially life-threatening hypoglycemia due to hyperinsulinemia.
The hyperinsulinemia that can occur with these therapies is also associated with an elevated risk of cardiovascular disease, a major killer of diabetics. Therefore, a need exists for antidiabetic drugs which do not increase circulating insulin concentrations.
A new class of compounds, thiazolidinediones, have been documented to effect antihyperglycemic activity by increasing insulin action rather than by promoting insulin secretion. Thiazolidinediones ameliorate insulin resistance and normalize plasma glucose and insulin (where elevated) without causing a hypoglycemic state, even at very high doses. The thiazolidinedione insulin sensitizers, e.g., ciglitazone, englitazone, pioglitazone, BRL 49653 (5-[[4-[2-(methyl-2-pyridinylamino)ethoxy]phenyl]methyl]-2,4-thiazolidined ione), and troglitazone, enhance insulin-mediated suppression of hepatic glucose output and insulin-stimulated glucose uptake and utilization by adipose tissue. Thiazolidinediones also change glucose transporter (e.g. Glut 4) expression to contribute to increased insulin responsiveness.